Plug-in connections have the advantage, as compared with screw connections, that the connection of lines is substantially easier, since in place of an often difficult and time-consuming screwing in at locations which are sometimes difficult to reach, a single insertion movement is sufficient. Plug-in connections of the mentioned type are already known from German Offenlegungsschrift No. 28 56 069, in which the receiving part is constructed as an adapter which permits plug-in connections to be effected with members which have a standardized threaded hole for a screw connection, for example braking cylinders. In such conventional couplings, however, the retaining ring is located near the rear end of the receiving part, which results in a relatively long length of the coupling.
A basic purpose of the invention is therefore to provide a coupling of the above-mentioned type having a length which is relatively short.